Last update January 20, 2022
If plug-in you've just installed doesn't show up on plug-in list in Studio One first of all make sure all Software Requirements are met by your setup.
Try out the solution described in this entry at our FAQ. It's possible that some system runtime libraries required by plug-in are missing. This concerns especially relatively fresh Windows installations.
Still no success? Open Studio One's Preferences and go to Locations tab. Then click Reset Blocklist button and restart the host.
if you're user of macOS 10.13 High Sierra (or newer) and utilize Audio Unit format of the plug-ins, check out this entry at our FAQ